Amateur radio antennas, such as those known in the art as Hex-beam antennas (sold by Traffie Technology of Ashby, Mass., and others), include a complex transmission line system to deliver RF power to driven elements of the antenna. The transmission line system is mounted to a mast of the antenna and is centrally located among a plurality of spreader arms extending outwardly from the mast. These antennas are popular due to their low cost and relative ease of installation. However, they are not without their problems.
Conventional transmission line feed systems are made of multiple lengths of coaxial cable arranged in series, with feed points of the antenna's driven elements attached to the junctions between the various lengths of coaxial cable. Such a transmission line system is difficult to manufacture for a variety of reasons. The multiple lengths of coaxial lines must be provided in various specific lengths, and require numerous points of connection to be manually prepared and soldered, which is a labor intensive and time consuming task. In addition, each of the multiple lengths of coaxial cable must be sealed to prevent water infiltration. Moreover, a coaxial transmission line is non-balanced, whereas the driven elements of the antenna are balanced, thereby necessitating a balun at each feed point for more optimum performance. Furthermore, each of the driven elements pulls on the terminals of the coaxial feed line, thereby requiring a separate mechanical arrangement to absorb tension in the driven elements.
Thus, the need exists for a transmission line system that is easier to manufacture, more stable and reliable, and that is electrically balanced so that no balun is needed at each element to transmission line junction.